Fabíola Cardillo

IL-23 Provides a Limited Mechanism of Resistance to Acute Toxoplasmosis in the Absence of IL-12

IL-23 and IL-12 are heterodimeric cytokines which share the p40 subunit, but which have unique second subunits, IL-23p19 and IL-12p35. Since p40 is required for the development of the Th1 type response necessary for resistance to Toxoplasma gondii, studies were performed to assess the role of IL-23 in resistance to this pathogen. Increased levels of IL-23 were detected in mice infected with T. gondii and in vitro stimulation of dendritic cells with this pathogen resulted in increased levels of mRNA for this cytokine. To address the role of IL-23 in resistance to T. gondii, mice lacking the p40 subunit (common to IL-12 and IL-23) and mice that lack IL-12 p35 (specific for IL-12) were infected and their responses were compared. These studies revealed that p40−/− mice rapidly succumbed to toxoplasmosis, while p35−/− mice displayed enhanced resistance though they eventually succumbed to this infection. In addition, the administration of IL-23 to p40−/− mice infected with T. gondii resulted in a decreased parasite burden and enhanced resistance. However, the enhanced resistance of p35−/− mice or p40−/− mice treated with IL-23 was not associated with increased production of IFN-γ. When IL-23p19−/− mice were infected with T. gondii these mice developed normal T cell responses and controlled parasite replication to the same extent as wild-type mice. Together, these studies indicate that IL-12, not IL-23, plays a dominant role in resistance to toxoplasmosis but, in the absence of IL-12, IL-23 can provide a limited mechanism of resistance to this infection.

B cells modulate T cells so as to favour T helper type 1 and CD8 + T-cell responses in the acute phase of Trypanosoma cruzi infection

In this study, we have evaluated the production of pro‐ and anti‐inflammatory cytokines and the formation of central and effector memory T cells in mice lacking mature B cells (muMT KO). The results show that Trypanosoma cruzi infection in C57Bl/6mμ MT KO mice is intensified in relation to control mice and this exacerbation is related to low levels of inflammatory cytokines produced during the acute infection and the lower numbers of central and effector memory CD4+ and CD8+ T cells generated during the acute phase of the infection. In addition, a marked reduction in the CD8+ T‐cell subpopulation was observed in muMT KO infected mice. In agreement to this, the degree of tissue parasitism was increased in muMT mice and the tissue inflammatory response was much less intense in the acute phase of the infection, consistent with a deficit in the generation of effector T cells. Flow cytometry analysis of the skeletal muscle inflammatory infiltrate showed a predominance of CD8+ CD45Rb low in B‐cell‐sufficient C57Bl/6 mice, whereas the preponderant cell type in muMT KO skeletal muscle inflammatory infiltrate was CD4+ T cells. In addition, CD8+ T cells found in skeletal muscle from muMT KO infected mice were less activated than in control B‐cell sufficient infected mice. These results suggest that B cells may participate in the generation of effector/memory T cells. In addition and more importantly, B cells were crucial in the maintenance of central and effector memory CD8+ T cell, as well as the determination of the T cell cytokine functional pattern, and they may therefore account for critical aspects of the resistance to intracellular pathogens, such as T. cruzi.

The ACE inhibitors enalapril and captopril modulate cytokine responses in Balb/c and C57Bl/6 normal mice and increase CD4(+)CD103(+)CD25(negative) splenic T cell numbers.

Increasing evidence implies beneficial effects of angiotensin-converting enzyme (ACE) inhibitors beyond those of their original indications to control hypertension. One of the most attractive non-hemodynamic properties of ACE inhibitors is their ability to regulate cytokine production. The mechanism(s) underlying the role of ACE inhibitors on cytokine synthesis are not well understood but they have traditionally been attributed to the inhibition of angiotensin (Ang) II formation. In fact, it has been extensively demonstrated that ACE inhibitors decrease Ang II-induced production of proinflammatory cytokines and chemokines. However, it is not well described if inhibition of endogenous Ang II generation by ACE inhibitors modulates systemic cytokine production in mice. To verify that, in this work, we investigated the effects of treatment with the ACE inhibitors enalapril and captopril on cytokine synthesis in C57Bl/6 and Balb/c mice. Our results show that enalapril up regulates IL-10 produced by splenocytes from Balb/c and C57Bl/6 mice and captopril increased it only in Balb/c mice. Furthermore, CD4(+)CD103(+) presented increased IL-10 production after enalapril treatment. Enalapril as well as captopril short-term treatment enhanced IL-2 synthesis in Balb/c mice. Besides, enhanced IL-2 and IL-10 levels correlates with increased CD4(+)CD103(+)CD25(negative) T cells numbers in spleens from enalapril-treated mice.

Long-term administration of IgG2a anti-NK1.1 monoclonal antibody ameliorates lupus-like disease in NZB/W mice in spite of an early worsening induced by an IgG2a-dependent BAFF/BLyS production

The role of natural killer (NK) T cells in the development of lupus‐like disease in mice is still controversial. We treated NZB/W mice with anti‐NK1.1 monoclonal antibodies (mAbs) and our results revealed that administration of either an irrelevant immunoglobulin G2a (IgG2a) mAb or an IgG2a anti‐NK1.1 mAb increased the production of anti‐dsDNA antibodies in young NZB/W mice. However, the continuous administration of an anti‐NK1.1 mAb protected aged NZB/W mice from glomerular injury, leading to prolonged survival and stabilization of the proteinuria. Conversely, the administration of the control IgG2a mAb led to an aggravation of the lupus‐like disease. Augmented titres of anti‐dsDNA in NZB/W mice, upon IgG2a administration, correlated with the production of BAFF/BLyS by dendritic, B and T cells. Treatment with an anti‐NK1.1 mAb reduced the levels of interleukin‐16, produced by T cells, in spleen cell culture supernatants from aged NZB/W. Adoptive transfer of NK T cells from aged to young NZB/W accelerated the production of anti‐dsDNA in recipient NZB/W mice, suggesting that NK T cells from aged NZB/W are endowed with a B‐cell helper activity. In vitro studies, using purified NK T cells from aged NZB/W, showed that these cells provided helper B‐cell activity for the production of anti‐dsDNA. We concluded that NK T cells are involved in the progression of lupus‐like disease in mature NZB/W mice and that immunoglobulin of the IgG2a isotype has an enhancing effect on antibody synthesis due to the induction of BAFF/BLyS, and therefore have a deleterious effect in the NZB/W mouse physiology.

Immunity and immune modulation in Trypanosoma cruzi infection.

Chagas disease is caused by the protozoan Trypanosoma cruzi. The parasite reaches the secondary lymphoid organs, the heart, skeletal muscles, neurons in the intestine and esophagus among other tissues. The disease is characterized by mega syndromes, which may affect the esophagus, the colon and the heart, in about 30% of infected people. The clinical manifestations associated with T. cruzi infection during the chronic phase of the disease are dependent on complex interactions between the parasite and the host tissues, particularly the lymphoid system that may either result in a balanced relationship with no disease or in an unbalanced relationship that follows an inflammatory response to parasite antigens and associated tissues in some of the host organs and/or by an autoimmune response to host antigens. This review discusses the findings that support the notion of an integrated immune response, considering the innate and adaptive arms of the immune system in the control of parasite numbers and also the mechanisms proposed to regulate the immune response in order to tolerate the remaining parasite load, during the chronic phase of infection. This knowledge is fundamental to the understanding of the disease progression and is essential for the development of novel therapies and vaccine strategies.

Chronic Chagas' Disease: Targeting the Interleukin-2 Axis and Regulatory T Cells in a Condition for Which There Is No Treatment

CNPq/FIOCRUZ and Fundacao OctacilioGualberto, Faculdade de Medicina de Petropolis (FMP-FASE).

Scrutinizing the Biomarkers for the Neglected Chagas Disease: How Remarkable!

Biomarkers or biosignature profiles have become accessible over time in population-based studies for Chagas disease. Thus, the identification of consistent and reliable indicators of the diagnosis and prognosis of patients with heart failure might facilitate the prioritization of therapeutic management to those with the highest chance of contracting this disease. The purpose of this paper is to review the recent state and the upcoming trends in biomarkers for human Chagas disease. As an emerging concept, we propose a classification of biomarkers based on plasmatic-, phenotype-, antigenic-, genetic-, and management-related candidates. The available data revisited here reveal the lessons learned thus far and the existing challenges that still lie ahead to enable biomarkers to be employed consistently in risk evaluation for this disease. There is a strong need for biomarker validation, particularly for biomarkers that are specific to the clinical forms of Chagas disease. The current failure to achieve the eradication of the transmission of this disease has produced determination to solve this validation issue. Finally, it would be strategic to develop a wide variety of biomarkers and to test them in both preclinical and clinical trials.

Tolerogenic Dendritic Cells Reduce Airway Inflammation in a Model of Dust Mite Triggered Allergic Inflammation

Purpose The use of tolerogenic dendritic cells (TolDCs) to control exacerbated immune responses may be a prophylactic and therapeutic option for application in autoimmune and allergic conditions. The objective of this work was to evaluate the effects of TolDC administration in a mouse model of allergic airway inflammation caused by mite extract. Methods Mouse bone marrow-derived TolDCs were induced by incubation with granulocyte-macrophage colony-stimulating factor (GM-CSF) and dexamethasone, and then characterized by flow cytometry and cytokine production by enzyme-linked immunosorbent assay (ELISA). For the in vivo model of Blomia tropicalis-induced allergy, mice transplanted with antigen-pulsed TolDCs were sensitized intraperitoneally with B. tropicalis mite extract (BtE) adsorbed to aluminium hydroxide. After challenge by nasal administration of BtE, bronchoalveolar lavage fluid (BALF), lungs, spleen and serum were collected for analysis. Results Induction of TolDCs was efficiently achieved as shown by low expression of major histocompatibility complex (MHC) II, programmed death-ligand (PD-L) 2 and pro-inflammatory cytokine production, and up-regulation of interleukin (IL)-10, upon LPS stimulation in vitro. Transplantation of 1 or 2 doses of BtE-pulsed TolDCs reduced the number of inflammatory cells in BALF and lungs as well as mucus deposition. Moreover, compared to saline-injected controls, TolDC-treated mice showed lower serum levels of anti-BtE immunoglobulin E (IgE) antibodies as well as reduced Gata3 and IL-4 gene expression in the lungs and decreased IFN-γ levels in the supernatant of splenocyte cultures Transplantation of TolDCs increased the percentage of the regulatory T cells in the spleen and the lungs. Conclusions Preventive treatment with TolDCs protects against dust mite-induced allergy in a mouse model, reinforcing the use of tolerogenic dendritic cells for the management of allergic conditions.